Line drop compensator



Feb. 14, 1939. w. w. KUYPER 2,147,490

LINE DROP COMPENSATOR Original Filed Sept. 23, 1936 RESISTANCE POSITIVE REACTANCE ELEMENT: ADJUSTER.

8 NEGATIVf REACTA/VCE w EL EMENTI LEAD 30 2 T01 S G E PHASE T0 VOLTAGE MEASURING DEVICE (INDICATING 0R con/mar.)

Inventor- I William W. Kugper,

His Abtorneg.

Patented Feb. 14, 1939 UNITED STATES PATENT OFFICE LINE DROP COMPENSATOR William W. Kuyper, Lynn, Mass., assignor to General Electric Company, a corporation of New York Application September 23, 1936, Serial No. 102,221

Renewed June 15, 1938 15 Claims. (Cl. 171-119) My invention relates to line drop compensathe current and voltage are in phase with each tors and more particularly to improvements in other, and consequently the line current can be line drop compensators adapted for use with sintransformed in a simple straight-forward mangle phase feeder voltage regulators which are ner by means of current transformers and apconnected open-delta on three phase alternatplied directly to the line drop compensators. 5 ing current circuits. When the regulated feeder circuits are three- It is often desirable to know the voltage on a phase circuits, however, there has in the past circuit at a remote point to which it is not conbeen a considerable problem in connection with venient to run the wires of a voltage measuring the line drop compensators. This problem in part circuit. Usually the difference in voltage bearises from the fact that one of the simplest and I0 tween the remote point and the point at which easiest ways to regulate the voltage of such it is convenient to connect a voltage measuring circuits is by connecting two single phase regucircuit or device to the main circuit is caused by lators in open-delta to the three-phase circuit. the voltage drop in the main circuit between With such a connection, one regulator varies the these two points. This voltage drop is proporvoltage of one of the line conductors of the thrcel5 tional to the product of the current in the main phase circuit and the other regulator varies the circuit and the impedance of the main circuit voltage of another of the conductors of the threebetween the two points. The impedance usualphase circuit and due to the normal equilateral ly comprises a resistance component and a retriangle formed by the line to line voltage vectors 2 actance component, the voltage drops in which of a balanced voltage three-phase circuit no are 90 out of phase with respect to each other. regulator is needed in the third conductor and A line drop compensatoris a device for com proper operation of two regulators in two of the pensating a voltage measuring circuit for the conductors will maintain substantially balanced voltage drop in the main circuit between the line voltage on the three-phase circuit. The

: 5 points on the main circuit to which the voltage feeder regulators are usually variable ratio transmeasuring device is connected and a remote point formers of either the tap-changing type or inducon the main circuit, such for example as a sotion type, and they each consist essentially of called center of distribution. A conventional line a series Winding connected in one of the line drop compensator consists of a resistance eleconductors and an exciting or primary winding merit and a reactance element through which a connected between the conductor in which the "a current variable in magnitude and phase with series winding is connected and one of the other the current in the main circuit is passed. The circuit conductors. Consequently, in connectresistance and reactance elements are so adjusted ing a single-phase regulator to a single-phase with respect to the current passed through them circuit connection need only be made to two and with respect to the voltage of the voltage line conductors. Unfortunately, however, there measuring circuit that the voltage drops in these is at unity power factor on three-phase circuits elements bear the same relation to the voltage a 30 phase displacement between the line to applied to the voltage measuring circuit or deline voltage and the current in each of the lines vice as do the resistance and reactance voltage between which the voltage is measured. Consodrops in the main circuit to the voltage of the quently, if an ordinary line drop compensator is 4 main circuit. connected to carry current which varies in mag- One of the commonest uses of line drop comnitude and phase with the current in one of the pensators is in connection with feeder voltage lines of the three-phase circuit between which regulating systems. Most electrical distribution line and one of the other lines the voltage meassystems are provided with sub-stations in which uring circuit is connected, true line drop cornas are installed one or more feeder voltage regupensation will not be secured. lators. The sub-station is usually not located at Various ways of correcting for this 30' phase the center of distribution at which it is desired angle difference have been used in the past, but to hold rated voltage and consequently the conthey have all had disadvantages. One method trol circuits for the regulators have to be comhas been to use additional current transformers 5c pensated for the line drop between the regulators so interconnected as to produce a resultant curand the center of distribution. When the regurent, for application to the line drop compensalated feeder circuit is a single phase circuit, the tor element, which is shifted 30 in phase. Such application of line drop compensator-s is simple arrangements, however, are expensive as they 53 because at unity power factor on such circuits, require the additional current transformers and, 55

furthermore, they usually require connection to the third conductor of the three-phase circuit which is undesirable. Another way has been to keep the 30 phase shift, but vary the settings of the resistance and reactance elements so as to produce a resultant impedance of the line drop compensator which is shifted through a 30 angle. This, however, requires somewhat advanced calculation and is beyond the ability of most substation operators and power company linemen who are charged with setting the line drop compensators.

In accordance with my invention, I provide a line drop compensator which is adapted to secure its entire energization from a single current transformer connected-in one of the conductors between which and another of the conductors of a three-phase circuit the voltage measuring circuit is connected, and which has resistance and reactance elements which can be set directly in accordance with the resistance and reactance of the line whose drop is to be compensated for, just as with single phase compensators.

An object of my invention is to provide a new and improved line drop compensator.

My invention will be' better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring now to the single figure of the accompanying drawing, I have shown therein diagrammatically an embodiment of my invention in combination with a three-phase power circuit I and a voltage measuring circuit 2 which is connected to respond to the voltage between two of the lines of circuit l bymeans of a potential transformer 3. A current transformer 4 connected in one of the lines between which potential transformer 3 is connected serves to supply the operating current for my line drop compensator. The compensator is provided with two resistance elements 5 and 6 and two reactance elements I and 8. The resistance element 5 and the reactance element 8 are set directly for a numerical value corresponding to the resistance of the circuit I, just as the resistance element of any conventional line drop compensator adapted for single phase operation is set. Likewise, the reactance element 1 and the resistance element 6 are set directly for a numerical value corresponding to the reactance of circuit I, just as the reactance element of any conventional line drop compensator adapted for single phase operation is set.

While the resistance and reactance elements 5 and 8 may be set independently of each other and the reactance and resistance of elements 1 and B may be set independently of each other, it is preferable to provide a common resistance adjuster for simultaneously adjusting the elements 5 and 8. Such an adjuster is illustrated schematically at 9. Likewise, it is preferable that the elements I and 6 be capable of simultaneous adjustment by means of a common member which is shown schematically as the reactance adjuster 10. The resistance elements 5 and 6 maybe of any well-known type and are shown as ordinary rheostats. The reactance elements may also be of any well-known type, and they are shown by way of example as reactance transformers having relatively rotatable windings for varying their mutual inductance and thereby varying the voltage induced in their secondary windings by heir primary windings.

The energizing circuit for the elements of the.

be produced in resistance elements 5 and 6,.

which voltages are proportional to the product of the current in circuit I and the resistance and reactance values of the elements of the compensator.

The elements of the compensator are arranged to have their voltages inserted in the voltage measuring circuit 2 by means of a pair of transformers H and i2. Transformer I l is a variable ratio transformer having a 1:1 ratio tap l3 and a 1:.886 ratio tap M. The transformer l2 has a 2:1 ratio.

The connections between the resistance and reactance elements of the compensator and transformers II and 12 are controlled by means of switching apparatus which may consist of a plurality of separately operable switches but which preferably are combined by means of a common operating mechanism into a three-position adapter switch [5. In one position of this switch, the compensator is adapted for single-phase op eration, in a second position it is adapted for three-phase operation when the line current leads the line to line voltage by 30 and in the remaining position is adapted for three-phase operation when the line current lags the line to line voltage by 30. f

The operation of the illustrated embodiment of my invention is as follows:

With the switch l5 in the position shown, the compensator is adapted for single-phase operation in that the resistance and reactance elements 5 and I are connected in the voltage measuring circuit through a 1:1 ratio transformer by means of an element l6 of switch l5. An element I! of the switch l5 short-circuits the secondary winding of the 2:1 ratio transformer l2. With this setting of the adapter switch, the compensator is the equivalent of a conventional compensator, and the resistance element 5 and reactance element 1 when set to have values corresponding to the resistance and reactance of the circuit 1, will produce voltages in the voltage measuring circuit which have the same relation to the voltage of this circuit as the actual resistance and reactance drops in the main circuit i have with respect to the voltage of the main circuit.

The switch l5 has a reversing switch element l8 which connects the elements 6 and 8 to the transformer l2, thereby in effect short-circuiting them. This is in order to reduce to a minimum the losses in the compensator and the volt-ampere drain on the current transformer 4 during single-phase operation of the compensator.

It should, of course, be understood that with the potential transformer 3 and the current transformer 4 connected to the three-phase circuit as shown, the above arrangement will not give true line drop compensation because there is a 30 phase difference between the potential produced by the potential transformer and the current produced by the current transformer at unity power factor on circuit I. However, if the lower two conductors of the three-phase circuit l are imagined to be a single phase circuit in which 2,147,490 the current and voltage are in phase at unity power factor, then the device will give true line drop compensation for the single phase setting of the switch 15.

If now the switch I is moved to its mid-position, labeled three-phase lead 30, the switch element I6 will connect the resistance element 5 and the reactance element I to the 12.866 ratio tap on the transformer II, and the switch element I! will remove the short circuit about the 2:1 ratio transformer 12. If now the reactance element 8 has been so connected or adjusted that it has a negative sign with respect to the reactance element 1, the various resistance and reactance elements will have the following values when referred to the voltage measuring circuit 2.

First assume that the absolute numerical magnitudes of the resistance element 5 and reactance element 8 are 1 ohms and that the absolute numerical magnitude of the reactance element 1 and resistance element 6 are :2: ohms. Then the re-' sistance element 5 and reactance element I, when referred to the voltage measuring circuit 2, will be .8661' and .8661: because of the ratio of the transformer H. Similarly, because-of the 2:1 ratio of the transformer I2 and the connections of the switch elements I! and I8, the value of the resistance element 6 will be 53: and the. value of reactance element 8 will be r.

Now if R stands for the total resistance value necessary to secure true resistance compensation for any connection of the compensator and X stands for the total reactance value necessary to secure true compensation for any connection of the compensator, it is clear that for single-phase operation R=r and X=:L'. It can also be shown that when the current leads the voltage by 30 R should equal 1 From the preceding paragraph it will be seen that this is precisely what the compensator produces with the adapter switch IS in the mid-position because, when referred to the voltage measuring circuit 2, the sum of the two resistance elements 5 and 6 is .866r-l- A 1: (.866 being the same as the V72), while the sum of the two reactance elements 1 and 8 is .86612- 1'.

When the adapter switch i5 is moved to the right so as to give proper line drop compensation for 30 lag, the only difference in the connections is that reversing element l8 reverses the connections between the elements 6 and 8 on the one hand and the 2:1 ratio transformer l2 on the other hand. This causes resistance element 6 to insert a value corresponding to 1: in the voltage measuring circuit and causes the reactance element 8 to insert a value corresponding to 1'. This will then give true line drop compensation for this condition, because it can be shown that for 30 lag the proper value for R is .866r :c, and the proper value for X is .866a:+ r.

It will be observed that 0.866 is equal to the cosine of 30 degrees and 0.5 is equal to the sine of 30 degrees. The generalization can therefore be made that if the tap I4 on the transformer H has a value corresponding to the cosine of any angle 0 between the potential applied to the potential transformer 3 and the current in the current transformer 4 at unity power factor on the main circuit and if the ratio of transformer l2 corresponds to the sine of this angle, the compensator will give correct line drop compensation for any given angle.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications can be made, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a line drop compensator, a pair of opposite sign resistance and reactance elements, a voltage measuring circuit, and means for simul taneously reversing the signs of said elements with respect to said voltage measuring circuit.

2. In a line drop compensator, means for inserting in a voltage measuring circuit two resistance voltages which are proportional respectively to .866 of an amount of resistance line drop to be compensated and one half of an amount of reactance line drop to be compensated, and means for similarly inserting two reactance voltages which are proportional respectively to .866 of an amount of reactance line drop to be compensated and one half of an amount of resistance line drop to be compensated.

3. In a line drop compensator, means for inserting in a voltage measuring circuit two resistance voltages which are proportional respectively to .866 of an amount of resistance line drop to be compensated and one half of an amount of reactance line drop to be compensated, and means for similarly inserting two reactance voltages which are proportional respectively to .866 of an amount of reactance line drop to be compensated one half of an amount of resistance line drop to be compensated, said half valued voltages being of opposite sign.

4. In a line drop compensator, means for inserting in a voltage measuring circuit two resistance voltages which are proportional respectively to .866 of an amount of resistance line drop to be compensated and one half of an amount of reactance line drop to be compensated, and means for similarly inserting two reactance voltages which are proportional respectively to .866 of an amount of reactance line drop to be compensated and one half of an amount of resistance line drop to be compensated, and means for selective- 1y reversing the signs of said one half valued voltages.

5. In a line drop compensator, means for inserting in a voltage measuring circuit two resistance voltages which are proportional respectively to .866 of an amount of resistance line drop to be compensated and one half of an amount of reactance line drop to becompensated, means for similarly inserting reactance voltages which are proportional respectively to .866 of an amount of reactance line drop to be compensated and one half of an amount of resistance line drop to be compensated, said half valued voltages being of opposite sign, and means for reversing the signs of said half valued voltages.

6. In a line drop compensator. means for producing a pair of resistance voltage drops and a pair of reactance voltage drops, the voltage drop values in each pair being proportional respectively to the resistance and reactance components of an amount of line drop to be compensated. a voltage measuring circuit, means for inserting in said voltage measuring circuit .866

of the value of one of said resistance voltage drops and .866 of the value of one of said reactance voltage drops, and means for inserting in'said voltage measuring circuit one half the values of the remaining two voltage drops.

'7. In combination, an alternating current power line, a circuit for measuring thevol'tage of said ,line and a line drop compensator for compensating said measuring circuit for the voltage drop in said line produced in a given amount of the resistance and reactance of said line, said compensator having two resistance elements whose values are proportional respectively to said given amount of line resistance and line reactance and having two reactance elements Whosevalues are proportional respectively to said given amount of line reactance and line resistance, transforming means for connecting said elements in said voltage measuring circuit, and switching means for controlling the connections between said elements and said transforming means so as to secure true line drop compensation regardless of whether said power line is single or three-phase.

8. A line drop compensator having a pair of simultaneously adjustable resistance and reactance elements which may be set directly in accordance with the resistance of a power line, a pair of simultaneously adjustable reactance and resistance elements which may be set directly in accordance with the reactance of said power line, a voltage measuring circuit, and means including a three-position adapter switch for making varying connections between said elements and said voltage measuring circuit whereby in one position of said switch said compensator gives true line drop compensation for single phase circuits, in another position of said switch said compensator gives true line drop compensation for threephase circuits in which the line current lags the line to line voltage by 30 at unity power factor and in the remaining position of said switch said compensator gives true line drop compensation for three-phase circuits in which the line current leads the line to line voltage by 30 at unity power factor.

9. In a line drop compensator, means for pro- I ducing a pair-of resistance voltage drops which are respectively proportional in magnitude to the resistance and reactance component of an amount of line drop to be compensated, means for producing a pair of reactance voltage drops which are respectively proportional in magnitude to the reactance and resistance components of said amount of line drop to be compensated, a voltage measuring circuit, a pair of transformers for inserting said voltage drops in said circuit, and a three position adapter switch so arranged that in one position one of said resistance voltage drops and one of said reactance drops are inserted full value in said measuring circuit by one of said transformers, in the remaining two positions of said switch the remaining two voltage drops are inserted in said measuring circuit at half value by the remaining transformer while the ratio of the first transformer is so changed that it inserts .866 of the value of its associated voltage drops, said switch when it is moved from one to the other of said remaining two positions reversing the signs of said half valued voltage drops.

10. In a line drop compensator adapted for use with a three-phase power circuit, a control circuit which measures the voltage between two of the lines of said power circuit, resistance and reactance elements connected in said control circuit, means limited to a single current transformer for circulating in said elements an operating current which varies in accordance with the magnitude and phase of the current in one of said two lines, a resistance adjuster for making the resistance setting of said compensator di.

rectly in accordance with the resistance of said power circuit, a reactance adjuster for making the reactance setting of the compensator directly in accordance with the reactance of said power circuit, and means for so modifying the'connections between said elements and said control circuit as to secure true line drop compensation.

11. A line drop compensator comprising in combination a pair of resistance elements whose values are proportional respectively to the resistance and reactance of a given amount of line whose voltage drop is to be compensated, a pair of positive and negative reactance elements whose values are proportional respectively to the reactance and resistance of said given amount of line whose voltage drop is to be compensated, a transformer having a one to one ratio tap and a one to .866 ratio tap, a transformer having a two to one ratio, and multi-position switching means which in one position connects the resistance element which is proportional to the line resistance in series with the positive reactance element to said one to one ratio tap and short circuits said two to one ratio transformer, which in another position transfers the connections of said series connected elements to said one to .866, ratio tap, opens said short circuit and connects the remaining to elements in series to the primary winding of said two to one ratio transformer, and which in another position reverses the connections of said two to one ratio transformer.

12. A line drop compaisator for connection in a circuit for measuring the voltage between two conductors of a power line and for energization by a current derived wholly from one of said conductors comprising, in combination, an adjustable resistance drop compensator which is set directly in terms of line resistance, said resistance compensator containing an impedance element which is efiectively connected in said voltage measuring circuit, an adjustable reactance drop compensator which is set directly in terms of line reactance, said reactance compensator having an impedance element which is effectively connected in said voltage measuring circuit, and means including multi-position circuit controlling apparatus for selectively varying the circuit relationship be--' tween an impedance element of each of said compensators and the voltage measuring circuit, said apparatus having a first position for causing said compensator to give true line drop compensation for single phase power lines, said apparatus having a second position for causing said compensator to give true line drop compensation for three-phase power lines in which said conductor current lags said voltage between conductors by 30 degrees at unity power factor, said apparatus having a t-hirdposition for causing said compensator to give true linedrop compensation for three-phase power lines in which said conductor current leads said voltage between conductors by 30 degrees at unity power factor.

13. In a line drop compensator, means for inserting in a voltage measuring circuit compensator voltages composed of four voltage drop components, two of said components being-resistance voltage drops proportional respectively to 0.866 of a desired amount of resistance line drop compensation and 0.5 of a desired amount of reactance line drop compensation, the other two components being reactance voltage drops which are proportional respectively ,to 0.866 of said amount of reactance line drop compensation and 0.5 of said amount of resistance line drop compensation, means for simultaneously and proportionately varying the magnitudes of said 0.866 valued resistance voltage drop component and said 0.5 valued reactance voltage drop component so as to adjust the resistance compensation of said compensator, and means for simultaneously and proportionately varying the magnitudes of said 0.866 valued reactance voltage drop component and said 0.5 valued resistance voltage drop component so as to adjust the reactance compensation of said compensator.

14. In a line drop compensator having potential and current circuits energized by the potential and current of a main circuit which are out of phase by the angle 0 at unity power factor on the main circuit, means for inserting in said potential circuit compensator voltages composed of four voltage drop components, two of said components being resistance voltage drops proportional respectively to cosine 0 of a desired amount of resistance line drop compensation and sine 0 of a desired amount of reactance line drop compensation, the other two components being reactance voltage drops which are proportional respectively to cosine 0 of said amount of reactance line drop compensation and sine 0 of said amount of resistance line drop compensation.

15. In a line drop compensator having potential and current circuits energized by the potential and current of a main circuit which are out of phase by the angle 0 at unity power factor on the main circuit, means for inserting in said potential circuit compensator voltages composed of four voltage drop components, two of said components being resistance voltage drops proportional respectively to cosine 0 of a desired amount of resistance line drop compensation and sine 0 of a desired amount of reactance line drop compensation, the other two components being reactance voltage drops which are proportional respectively to cosine 0 of said amount of reactance line drop compensation and sine 0 of said amount of resistance line drop compensation, means for simultaneously and proportionately varying the magnitudes of said cosine 0 valued resistance voltage drop component and said sine 0 valued reactance voltage drop component so as to adjust the resistance compensation of said compensator, and means for simultaneously and proportionately varying the magnitudes of said cosine 9 valued reactance voltage drop component and said sine 6 valued resistance voltage drop component so as to adjust the reactance compensation of said compensator.

WILLIAM W. KUYPER. 

